With the methods most commonly used for making a static steerable connection placed at the end of a drill string, the length of the bent housing cannot be reduced without compromising the life of the thrust bearing used as support for the drilling tool. A transmission of weight on the tool is effected, described as WOB (“weight on bit”). It follows that wide connection angles are necessary to be able to obtain the deviations or curvatures usually called “Build-Up Rate” (BUR), which are sought in the applications concerned.
International application WO 90/07625 and U.S. Pat. Nos. 6,244,361, 6,640,909, 6,808,027 and 6,847,304 describe architectures of trajectory control devices of boring rods comprising a flexible shaft, employing a method called “static bit force (rotary traversing shaft)/Point the bit.”
International application WO 90/07625 and U.S. Pat. Nos. 3,677,354, 5,305,838, 5,307,885, 5,353,884, 5,875,859, 6,808,027 and 6,847,304 describe, furthermore, so-called “internal” coupling means for forcing the steering of a transmission shaft used in such an application.
EP Patent 0,744,526 and U.S. Pat. No. 4,947,944 describe so-called “external” coupling means for a set of components of drill string and drilling tools.
International application WO 03/102353 certainly describes a drilling device containing a component for enabling and controlling the deviation of the shaft and drill bit. However, the device described in this document must contain two concentric tubular elements, respectively outer and inner, which can take a position in which they are uncoupled from one another, in order to make possible the rotation of the inner tubular element, while rotation of the outer tubular element is prevented.
The publication of US Patent Application No. 2005/0173155 describes an assembly of drilling means in which a locking means is provided to transmit to the shaft a torsional moment generated by the case or housing disengageably.
According to that state of the art, means were not available for steering drilling tools in all the required configurations.
Therefore, no universal steerable connection exists at present, in the sense understood in the conditions referred to above.
Now, it appeared useful to have such means available, advantageously with the ability to place them on the existing equipment, and it also appeared desirable for the manufacture and maintenance of those new means sought to be simple to carry out at a reasonable cost, in order to reduce the cost per meter drilled, while improving the precision of drilling and offering greater trajectory flexibility and the longitudinal compactness desired, in order to bring the measurements of the drilling tool/bit as close together as possible.
The invention makes it possible to introduce solutions for these expectations and to provide devices and operating means that can respond to these objectives as well as others, which will emerge in light of the following description, accompanying drawings and attached claims.
The present invention is, therefore, intended to create a device for steering a drilling tool (bit, PDC, drill, etc.), said device being usable in different variations adaptable to needs and, furthermore, easy to operate everywhere. In addition, its maintenance is easy and the lifetime of its most stressed parts is also improved, considering that the dissymmetry between upstream and downstream of the device is taken into account, namely, between the low end of the main drill string or BHA (Bottom Hole Assembly) and the drilling tool/bit, respectively.